Access controls from user control using jquery on Default.aspx

Question

I am using jquery to send data to my dbase at the backend. I have a user control with textboxes on it. JQuery does not seem to get the values and I end up with The name 'thisID' does not exist in the current context (thisID being an input box)

data: '{projectID: "' + $("#<%=thisID.ClientID%>")[0].value + '"}',

I have my javascript on default.aspx and the texboxes are on a user control.

Thanks